Lesser Scaup

Aythya affinis

One of the most numerous and widespread diving ducks in North America, especially on inland waters. Can be very active when feeding, diving and surfacing repeatedly. In winter often seen on lakes and bays in dense flocks, numbering hundreds or even thousands, and often with no other species of ducks associated with them. The two species of scaup sometimes occur in the same places, but they tend to keep to themselves rather than mixing freely.

Conservation status

Although it is still abundant, the total population has declined significantly in recent decades, and the causes are not well understood.

Marsh ponds (summer), lakes, bays, estuaries. Summers around large marshes in prairie or forested regions. Winters on lakes, reservoirs, rivers, sheltered areas of coastal bays. Overlaps extensively with Greater Scaup, especially in winter, but at that season the Lesser is far more likely to be found on freshwater lakes and ponds well inland.

One of the most numerous and widespread diving ducks in North America, especially on inland waters. Can be very active when feeding, diving and surfacing repeatedly. In winter often seen on lakes and bays in dense flocks, numbering hundreds or even thousands, and often with no other species of ducks associated with them. The two species of scaup sometimes occur in the same places, but they tend to keep to themselves rather than mixing freely.

Photo Gallery

Feeding Behavior

Forages by diving and swimming underwater; sometimes by dabbling or up-ending in shallow water. Sometimes feeds at night.

Eggs

9-11, sometimes 8-14. Olive-buff. Incubation is by female only, 21-27 days. Young: Leave nest shortly after hatching, go to water. Young are tended by female but feed themselves. 2 or more broods of young may join under care of several adult females. Age at first flight 47-54 days after hatching.

Young

Leave nest shortly after hatching, go to water. Young are tended by female but feed themselves. 2 or more broods of young may join under care of several adult females. Age at first flight 47-54 days after hatching.

Diet

Includes mollusks, plant material. Diet varies with season and habitat, but animal matter may predominate, especially mollusks such as clams and snails, also aquatic insects, crustaceans. Also eats plant material such as stems and leaves of sea lettuce, pondweeds, wild celery, plus seeds of pondweeds, sedges, grasses, and others. Birds on the Great Lakes may feed heavily on the introduced zebra mussel.

Nesting

Probably first breeds at age of 2 years in most cases. Elements of courtship display by male include a shake of the head, followed by throwing the head far back and bringing it forward very quickly; exaggerated bowing movements; ritualized preening. Some displays may be performed underwater. Nest site is usually on dry land close to water, often on islands in lakes, surrounded by good cover of vegetation. Stands of bulrush in marshes especially favored. Nest is a slight depression with addition of some dry grass, lined with down.

How climate change could affect this bird's range

In the broadest and most detailed study of its kind, Audubon scientists have used hundreds of thousands of citizen-science observations and sophisticated climate models to predict how birds in the U.S. and Canada will react to climate change.

Lesser Scaup

Each map is a visual guide to where a particular bird species may find the climate conditions it needs to survive in the future. We call this the bird’s “climatic range.”

The colors indicate the season in which the bird may find suitable conditions— blue for winter, yellow for summer (breeding), and green for where they overlap (indicating their presence year-round).

The darker the shaded area, the more likely it is the bird species will find suitable climate conditions to survive there.

The outline of the approximate current range for each season remains fixed in each frame, allowing you to compare how the range will expand, contract, or shift in the future.

The first frame of the animation shows where the bird can find a suitable climate today (based on data from 2000). The next three frames predict where this bird’s suitable climate may shift in the future—one frame each for 2020, 2050, and 2080.

You can play or pause the animation with the orange button in the lower left, or select an individual frame to study by clicking on its year.

The darker the color, the more favorable the climate conditions are for survival. The outlined areas represent approximate current range for each season. More on reading these maps.